Show ``quote`` and ``availability`` in the public profile.

https://github.com/madewithbytes/us_ignite/issues/204

These two fields are shown in the profile.
Add mechanics to validate user profile ownership.

https://github.com/madewithbytes/us_ignite/issues/204

``profile.is_owned_by(user)`` determines if the user
is the owner of the given ``profile``.
Unify hub membership and ownership in one field.

https://github.com/madewithbytes/us_ignite/issues/204

The fields have been unified so they are more relevant.